Dart IRS

72 Demon, If you remember the jag has a lower torque arm, a lower control arm and uses the half shaft as the upper arm so it has a thrust load on the u joints. I think that's the way old corvettes were too. I'm not sure if the u joints are ready for that kind of abuse, the jag 4.2 wasn't a barn burner.
John's cars in Texas made a conversion for a Shivvee, but then they didn't make a lot of torque either.
Jag IRS still looks great in street rods!